The ATLASGAL survey: a catalog of dust condensations in the Galactic plane

Csengeri, Tímea and Urquhart, J. S. and Schuller, F. and Motte, F. and Bontemps, S. and Wyrowski, F. and Menten, K. M. and Bronfman, L. and Beuther, H. and Henning, Th. and Testi, L. and Zavagno, A. and Walmsley, M. (2014) The ATLASGAL survey: a catalog of dust condensations in the Galactic plane. ASTRONOMY & ASTROPHYSICS, 565. ISSN 0004-6361

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Abstract

Context. The formation processes and the evolutionary stages of high-mass stars are poorly understood compared to low-mass stars. Large-scale surveys are needed to provide an unbiased census of high column density sites which can potentially host precursors to high-mass stars.Aims. The ATLASGAL survey covers 420 sq. degree of the Galactic plane, between −80◦ < ℓ < +60◦ at 870 μm. Here we identify the population of embedded sources throughout the inner Galaxy. With this catalog we first investigate the general statistical proper- ties of dust condensations in terms of their observed parameters, such as flux density and angular size. Then using mid-IR surveys we aim to investigate their star-formation activity and the Galactic distribution of star-forming and quiescent clumps. Our ultimate goal is to determine the statistical properties of quiescent and star-forming clumps within the Galaxy and to constrain the star-formation processes.Methods. We optimized the source extraction method, referred to as MRE-GCL, for the ATLASGAL maps in order to generate a catalog of compact sources. This technique is based on a multi-scale filtering to remove extended emission from clouds to better determine the parameters corresponding to the embedded compact sources. In a second step we extract the sources by fitting 2D Gaussians with the Gaussclumps algorithm.Results. We have identified in total 10861 compact sub-millimeter sources with fluxes above 5σ. Completeness tests show that this catalogue is 97% complete above 5σ and > 99% complete above 7σ. Correlating this sample of clumps with mid-infrared point source catalogues (MSX at 21.3 μm and WISE at 22 μm) we have determined a lower limit of 33% that are associated with embed- ded protostellar objects. We note that the proportion of clumps associated with mid-infrared sources increases with increasing flux density, achieving a rather constant fraction of ∼75% of all clumps with fluxes over 5 Jy/beam being associated with star-formation. Examining the source counts as a function of Galactic longitude we are able to identify the most prominent star forming regions in the Galaxy.Conclusions. We present here the compact source catalog of the full ATLASGAL survey and investigate their characteristic proper- ties. From the fraction of the likely massive quiescent clumps (∼25%) we estimate a formation time-scale of ∼ 7.5 ± 2.5 × 104 yr for the deeply embedded phase before the emergence of luminous YSOs. Such a short duration for the formation of high-mass stars in massive clumps clearly proves that the earliest phases have to be dynamic with supersonic motions.

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